Polyester-carbonates are well known high molecular weight thermoplastic materials which exhibit many advantageous properties. These properties render the polyester-carbonate resins useful as high performance engineering materials.
However, one of the significant problems associated with the use of polyester-carbonate resins, particularly in high temperature environments, is the tendency of polyester-carbonates to undergo hydrolytic degradation. It is known in the prior art that the addition of certain additives to plastics, such as polycarbonates, results in compositions exhibiting increased resistance to hydrolytic degradation. Examples of such additives are found in U.S. Pat. Nos. 3,839,247; 4,076,686 and 4,138,379. These additives are generally quite useful, and have extended the uses of plastics, such as aromatic polycarbonates, into areas requiring increased levels of hydrolytic stability. However, certain properties of plastics, e.g., polycarbonate resins, can be detrimentally affected by the addition of these additives. Thus, in the case of aromatic polycarbonate resins, the presence of these additives can bring about haze in the polycarbonate article or detrimentally affect the color of the polycarbonate article.
There thus exists a need for polyester-carbonate compositions which exhibit improved hydrolytic stability while at the same time retaining all of the advantageous properties of unmodified polyester-carbonate resins. It is an object of the instant invention to provide such a polyester-carbonate composition.